The present invention relates to a floating-tupe anti-oil anti-impact anti-wave barrier.
Configurations of oil fences for preventing oil which has flowed out onto the sea from dispersing are largely different depending upon marine phenomena at the sea region where the oil fence is to be used, transportation equipment for the oil fence, materials of the oil fence, etc. However, in general, an oil fence having a desired length can be constructed by connecting oil fence units by means of water-proof flexible connecting members, each oil fence unit being formed of a float having a given length extending in the longitudinal direction and having an oil leakage preventing plate provided at its bottom along the longitudinal direction of the float.
When an oil outflow accident has occurred, th oil fence is transported to that sea region of the accident and is extended so as to encircle the outflow of oil, and the oil fence extended on the sea can be anchored without drifting because the oil fence has anchoring chains provided with weights mounted at the bottom of the oil leakage preventing plate. However, in the case of such prior art oil fences art, it may possibly happen that the captured outflow of oil escapes by passing under the oil leakage preventing plate due to the effects of waves and the tide.
Inherently, the oil fence is required to function to prevent the encircled oil from flowing out of the oil fence even under the effects of waves and the tide, but it is very difficult to prevent the oil from flowing out of the fence, and especially from passing under the oil fence.
As a result of experiments it has been proved that in the case of the conventional oil fence, leakage of oil would begin at a tidal current of 0.36 m/s (about 0.7 knots). This is caused by the fact that oil captured and pooled on the upstream side of the oil fence is converted into oil drops by tangential forces between the water and oil due to motion of water caused by waves or a tidal current, and that these numberless oil drops are driven by the tidal current and thus drift to the downstream side of water passing beneath the bottom of the oil fence.
As a solution for intercepting the oil passing under the oil fence in the form of oil drops, there have been devised methods of designing the oil fence to have a deep draught, of extending the oil leakage preventing plate downwards to a deeper extent, or of disposing oil fences in a plurality of rows at given intervals. However, in the case of the former two methods, a resistance force of the tidal current against the oil fence is so increased that it becomes difficult to extend the oil fence at a predetermined position, and if the oil fences are equipped in a plurality of rows according to the last method, for instance if the oil fences are extended in two parallel rows, depending upon the size of the oil drops and the speed of the tidal current it may happen that a part of the oil drops which have passed under the inner oil fence further arrive at the bottom of the outer oil fence and thus flow out of the oil fences. To extend the oil fences on the sea in three or more rows for avoiding the above disadvantage, is very troublesome, takes a substantial time for the extension and removal of the oil fences, and is very difficult in operation when wind and waves are even slightly strong.
In addition, the above-described prior art oil fence is liable to be destroyed when it strikes against a ship, a drifting object, etc., and further it is liable to be damaged due to repeated fatigue caused by waves.